Technical Field of the Invention
The present invention is directed to pneumatic artificial muscle actuators including embedded sensors that enable control of the actuators in real time.
Description of the Prior Art
Pneumatic artificial muscle (PAM) actuators are used to provide mechanical actuation in various fields, such as, robotics. The actuator typically includes a cylindrical tube extending along an axis, sealed at both ends, formed from an elastic material, such as rubber or silicon. A pneumatic inlet is provided to enable a fluid, such as a gas or liquid to be injected into the tube causing the tube to expand. The tube also includes flexible, but inextensible fibers or other material that prevents the tube from expanding along the axis. Typically, the fibers are fastened at each end of the tube. As a result, when air is injected into the inlet, the tube expands radially, in a direction transverse to the axis and contracts in length along the axis. When the air is released, the tube contracts radially and extends axially. In this way, the actuator can be used to cause a device, such as a robotic arm to move.
One of the drawbacks of these pneumatic actuators is that they can be difficult to control with respect to position (contraction length) and force (contraction force) due to their inherent nonlinear behavior. Extrinsic sensors, for example, located on the joint or elsewhere on the device, external to the actuator can be used. However, these extrinsic sensors make the system bulky, heavy, and complex, outweighing any potential advantages of using relatively small and light weight pneumatics for actuation.